Plating process



Pate ted Aug. 26, 1930 v UNITE STATES PATENT. osFics IBA'IIS'J'. B. naunis'nn, or INDIANAPOLIS, mnrama, Assnmon 'ro METALS rnorncr101; ooarona'non, or mmmarorrs, INDIANA, A conronarron or INDIANA 2LA'1'ING PROCESS This invention relates to plating processes; and it comprises a process of electroplating iron and steel obj eots with other metals wherein the object is madean anode in a solution of 5 chromic acid and a flow of current maintained until a brownish film coating forms and is then plated with a metal other than chromium, such as nickel, the brow'nfilm be- I ing sometimes removed before plating and sometimes not; all as more fully hereinafter set forth and as claimed.

. As is well known, it is diflicult by the ordinary plating processes to deposit various metals, such as nickel, as coatings of any sub- 5' stantial thickness with sul'ficient cohesion to the base to permit much, if any, stamping or punching o the coated base. The reason for this behavior is variously explained as being "hydrogen adsor tion, internal strains in the so coating, etc. atever the reason, the peelinglof nickel and other coatings is notoriously a 'fliculty in the art.

In a prior patent'to one Pierce 1,645,927, there is described and claimed a method of fixing chromium to iron and steel wherein the iron or steel is made an anode in a solution of CrO or the ordinary chromium plating bath, prior to depositingthe chromium coating. The anodic treatment of the object is quite brief and is not sufiicientl long to produce any visible change in the iron surface. Chromium plating baths have extremely oor throwing power and the advantage of the Pierce process is apparently that it oxidizes the whole surface sufiiciently to obviate local electrochemical difierences' local couples. So to speak, the whole surface is made equally difficult to late. a

This ierce process is applicable only to chromium plating; but I have discovered that I canv use alike process in lating iron or steel with other metals than 'c romium with advantageous results. The most commercially advantageous results'are in nickel plating but the advantage exists in the case of many other metals. V

In this modification of the Pierce process under. the resent invention the suitably cleaned meta article, which is usually iron or steel is made an anode-ins solution-of chromic Application filed Kay 10, 1929. Serial 110.38%,184. A

acid (CrO and operation is continued under current until a distinct brown film forms. A chromic acid bath of about 21 B. and con taining 240 grams er liter of CrO with about 2.5 grams of S6 per liter and 5 grams (lr O er liter serves well for my purposes. Other JrO baths may be used but. one of the stated concentrations and roportions I reard as advantageous. oncentrations of O ranging between zero and 50 grams per 00 liter have been used; but it has been noted that the presence of high proportions of sul.- fates causes considerable etching. Sometimes this is desirable but commonly it is not. Concentrations ofCrO as low as 100 grams per e5 liter have been used buthi herconcentrations are in general more desira 1e. Saturated so-. lut-ions have been used with satisfactory results. In the present operation chromate and bichromate solutions may be used although I r regard CrO as much more satisfactory. The current conditions should be such as to give free gassing- A temperature of 25 C. and a current density of 1 or 2 amperes p square inch of metal surface serves well. he time required to produce a good brown film varies with the particular steel or iron treated but is usually from 5 to 25 minutes.

- 2 After this treatment the object can be rinsed and transferred directly to a plating'bath and $0 plated in the usual way. Or, the film may firstbe removed either mechanically as by scrubbing the object with the aid of fine pummestone, or chemically by means of dips of concentrated sulfuric ornitric acid& I ordinarily remove the film. v

The nature of the brown film is not known. Rinsin the filmed object will remove a portion of the film but to remove all requires either the use of a brush or a swab with 0011-.

siderable scrubbing orimmersion in concentra'ted nitric or's'ulfhric' acid. Even after coating to the underlying steel is sufiicient the object a cathode in a plating bath to plate to permit a large amount of mechanical work a metal thereon.

on the coated metal; stamping and punching of the sheet for example.

The reason for the advantageous results secured in a plating operation following this anodic treatment of iron and steel in CrO is not known. It may, or may not, be due to equalization of carbon content over the treated surface or to the removal of undesirable impurities from the surface layer. As is well known, the carbon in iron and steel objects .is not in homogeneous distribution and also rolling scale, molding sand or even dissolved gases are often present on or near the surl'ace.

The present process is particularly applicable in the production of nickel or other metal coatings on objects which are to be sub- .--.equently chromium plated; for instance, steel or iron objects carrying a layer of chromium with an intermediate linking layer of nickel. The nickel plated object" may be chromium plated in any of the usual ways.

Steel objects coated with nickel, or with nickel and chromium, according to the present process 'ma" be twisted to the breaking point, punched ground, hammered, etc. without lifting or peeling the coating. iioilol' tubes coated with chromium with an intermediate coating of nickel have been flanged into headers without destroying or cracking the coating. X

The present process may be applied in the direct plating of iron and steel with chromium; the iron or steel being made an anode in a chromic acid solution until a brown film forms and then plated with chromium in the usual chromic acid bath. But I regard the invention as more particularly advantageous in the production of coherent coatings of nickel and metals other than chromium.

What I claim is I 1. In electroplating iron and steel articles with other metals, the'process which comprises making the articles an anode in a (110 bath sufliciently long to produce a brown film coating and thenplating a metal thereon.

2. 1n electroplating ironand steel surfaces with other metals, the process which comprises making the article an anode in a CrO bath sufiiciently long to produce a brown film coating and then plating the nickel.

3. In electroplating iron and steel articles with other metals, the process which comprises making the article an anode in a CrO bath sufliciently long to produce a brown film coating, then plating with nickel and finally plating with chromium.

41:. In. electroplating iron and steel objects, the pi ocess which comprises making the article an anode in a 010 bath suflieiently long to produce a brown film coating, removing a major portion of this film and then making In testimony whereof, I have hereunto affixed my signature.

BATIST R. HAUEISEN.

Ill) 

